Dry kiln



Feb. 10, 1953 R. A. slMMoNs DRY KILN Filed Sept. l, 1951 3 Sheets-Sheet 1 no N g1 9 1 N N m ro (D t0 Lo t; JN N co N N N .-A A l.. .N 1, e

: l 'H 'l l J INVENTOR. N R. A. SIMMONS ATTORNEY Feb. 10, 1953 R. A, slMMONs 2,627,671

A DRY KILN Filed Sept. l, 1951 5 Sheets-Sheet 3 W NHHII. Ml 25 l l l w \\\\\\\\\\\\\\\\\\\\\\\\\\fx if f RA. SIMMONS BY l y ATTORNEY Patented Feb. 10, 1953 UNITED STATES PATENTv OFFICE DRY KILN R. A. Simmons, Vernonia, Oreg. Y y Application September 1, 1951, Serial No. 244,817

' iciai'ms. (01.34-191) l This invention relates in general to dry kilns, and, in particular, to kilns for drying lumber, especially dry kilns for lumber in which the drying currents of air pass in a more or less horlzontal direction through the stacked lumber and in which the passage of air is reversed from time .to time so that the drying will take place uniformly. y

One of the objects of the invention is to provide an improved dry kiln in which the 'now of the drying currents of air and the reversal of the direction of the same will be controlled in a very easy and in a very simple manner.

Another object of the invention is to provide an improved dry kiln in which the delivery oi air into, and the Withdrawal of air from the kiln, regardless of the direction of passage of air through the lumber, will occur at the top ci the kiln, thus enabling the floor ofthe kiln to be at ,ground level as a convenience in moving cars of lumber into and out of the kiln.

A related object of the invention is to provide an improved lumber kiln in which control ofthe humidity and temperature of air in the kiln, as well as control of air movement, will all be regulated from the top of the kiln.

-An additional object of the invention is to provide a drykiln of simple. and practical construction having a forced air circulation controlled in a simple and practical manner, and in which the air currents and the air circulation will always be uniform throughout the entire length of the kiln.

The manner in which these objects are attained, together with incidental advantages, and

Fig. 2 is a similar longitudinal sectional elevatien or" the kiln taken-on line 2--2 of Fig. 3;

Fig. 3 is a plan section taken on lines '3--3 of Fig. 4 is a fragmentary enlarged sectional elevation corresponding in part to Fig. 1; and

Fig. 5 is a considerably enlarged vertical transverse section on line 5-5 of Fig. 3.

' The kilnincludes a pair of side walls lil and .I I, having no openings, a pair of end Walls I2 and I3, at least one of which has a door (not shown) to permit carloads of lumber L, (such a carloadbeing indicated in broken lines in Fig. 5)

to be moved into and out of the kiln, and-a ceiling wall I4.

Along each side ofthe ceiling It is a row of slot openings I5 of identical size andV equally spaced apart. Each slot opening extends a short distance inwardly and transversely from the side edge of the ceiling. The purpose of these slot openings l5 is toenable the drying air to be passed into; the kiln through vtheslot openings along one side and then to-V be withdrawn from the kiln through the slot openings along the other side, as will presently appear.

Two pairs of airducts I6, Il and' I, I9 are positioned above the ceiling wall Ill of `the-kiln as shown in Fig. 3, so as. tov extend entirely over the slot openings I5, the air ducts of each pair thus extending along on opposite sides of the ceiling .wall I4. Preferably these four airducts are identical in size and shape. The air ducts along each side come together at the approximate longitudinal middle point along the kiln. Each of these ducts constitutes a housing wth side walls and a sloping roof. The roofs of the ducts have a constant'downward slope from the end of the duct adjacent van end of the kiln to theopposite end of the duct vor the longitudinal middle point of the kiln, as shown in-Fig. 1. y

A pair of air chambers 20 and 2 I, located above the ceilingwall respectively at oppositeends of the kiln, connect the pairs of air ducts at the ends of the kiln. Each chamber has ay pair oi' ports 22 connecting the chamberwith the adjacent ducts respectively, and an air circulating -ian 23 `is located in each port. YPreferably the ports22 vare circular, having adiameter-only slightly greater Athan the diameter of the fans 23 located within the ports, and also preferably the area .of each port 22, and the corresponding larea oi eachzfan 23, approximately equals the total: area" ofzfhe slot openings I5 covered by. each-duct: The fans 23 are driven by electric motors 2li through the medium of suitable reduction drives, the ian motors being located in a motorroom 25, behind each .air chamber, and' the fan shafts extend Vthrough the air chambers and are supported in suitable bearings A(not shown). fReversible :controls (not shown) for the fan motors 2liv are provided. in the motorroomland the fan motors lare so arranged that the two fans of each air chamber will be Id riven in opposite directions.V

Thus, as indicated by the arrowsl in, Fig. 5, the fans during one period of operation are operated `to draw the air` from the ducts I6' and I8 into the chambers 2i) and 2I.respectively and. to drive the airthence into the. ducts Il and I9 respectively. Similarly, when the operation of the fans is reversed, air is drawn from the ducts l1 and i9 and forcibly delivered into the ducts IS and i8.

An air inlet 26 (Figs. 1, 2 and 4) is located on top of each of the ducts I6, l1, i8 and I9. The purpose of these inlets is to permit fresh air from the outside to be drawn into the ducts and thence into the kiln. The air inlets 26 have hinged covers or lids with upstanding arms which are connected by linkage to lever arms operated by diaphragm-controlled motors, one of which is indicated at 21 in Fig. 1. Whenever the air pressure within the duct is less than the atmospheric pressure outside of the kiln, these motors 27 will operate to cause the air inlets 26 for the two ducts on the suction side of the kiln, that is to say, the two ducts from which `air is being drawn from the kiln into the respective air chambers, to open. This allows some fresh air to be mixed with the air withdrawn from the kiln before such air is returned into the kiln. Meanwhile the inlets 26 on the opposite ducts, that is to say, the ducts into which the air 4from the chambers is driven and from which the air then moves down into the kiln, are kept closed. While only `one inlet 26 is shown on the roofrof `each duct in the drawings, it may be desirable to Vhave a plurality of such inlets `on each duct in the case of a very large kiln. In such event the inlets 26 on each duct are connected together so as to be operated in unison in the same manner.

A plurality of ventilators 28 (Figs. 2 and 5) are located along the center line of the ceiling between the ducts of each pair and are spaced apart equal distances throughout the length of the kiln.' Each ventilator 28, like the air inlets 26, has a `lid or cover with an upstanding arm. The arms of the covers of the ventilators are connected by suitable linkage lso that all the `ventilators 28 will be opened and closed simultaneously. The purpose of these central roof ventilators 28 is to allow air to be exhausted or discharged from the kiln whenever the kiln air becomes too hot or too humid, and vthese ventilators, due to their central position, will discharge the vair from the -top central portion of the kiln. The opening 'and closing of these ventilators 28 is done by suitable motonindicated at 29 -in Fig. 2, -which `in turn is controlled by an automatic temperature and humidity control regulator of a type which is well known and extensively used and which therefore need not be described.

Bailies 39 and 3l l(Figs. 2 and 5), extending longitudinally ofthe kiln and parallel to the side walls, are suspended from the ceiling wall in the relative positions illustrated in Fig. 5, thus being positioned inside the innerends `of lthe slot openings l5. These baffles extend down a short distance from the ceiling and their purpose is to prevent any short-circuiting of the air currents at the top of the kiln. Thus-the incoming air currents passing rdown through the slot openings l at one-side ofthe kiln will be required to pass down into the `kiln `first before moving laterally across the kiln to theother side and thence moving up and out of the kiln vthrough the slot openings in the ceiling on. the other side of the kiln. Preferably also correspondingv lower bailles 32 and 33 (Fig. 5) extend a short distance upwardly from. the oor of the kiln in substantial vertical alignment with the ceiling bailles and 3l. These lower `baiiles prevent cross currents of air occuring along the kiln hoor and under the cars which carry rthe'ilumber. .The lumber `is carried on cars in the usual manner and these cars move on rails 34 provided on the floor of the kiln. The lumber is stacked on the cars in horizontal layers as is customary. Consequently the drying currents of air in the kiln pass crossways through the lumber stacks and between the layers of lumber.

Steam heating pipes 35 and a main steam feed pipe 36 (Fig. l3) extend along both sides of the kiln below the slot openings l5 and between the side walls and the baffles 3B or 3l. These steam pipes are for the purpose of heating the kiln air. Perforated steam pipes or spray pipes 3l are similarly positioned and serve the purpose of providing necessary moisture for the kiln air. As is well known it is necessary to have some humidity in the kiln air in order to prevent the lumber from drying out too rapidly. The heating pipes as well as the spray pipes are all supported on suitable hangers.

Should the air in the kiln become too humid or should the temperature of the. kiln air become higher than that desired, the temperature and humidity control will cause the ceiling ventilators 28 to open. rl`his opening of the ventilators 28 will allow some of the air from the kiln along the central tcp portion of the kiln to exhaust through the ventilators. The exhausted air will ultimately be replaced by fresh air drawn in through the air inlets 2t in the suction ducts on one side of the kiln.

The manner in which my improved kiln operates will `be understood from the preceding ydescription. The drying current-s of air, entering the kiln through the slot openings, along one side of the kiln ceiling pass downwardly and then laterally or crossways through the lumber stacks and then out through the slot openings in the ceiling on the other side of lthe kiln, and'from time to time the direction of the air currents is reversed. If the air becomes too hot Vor too humid Asome Lof the fair will be exhausted through the central 'ceiling ventilators 28, as described, 'but this will occur without 'disturbing the drying process, and the exhausted air will be replaced by the out-side air drawn into the duets on' one side. The outsideair is mixed with .the other air from the kiln 'before being drawn into the kiln, and the :outside lair passes the heating pipes as it goes into the kiln. Thus there is no possibility of any chilling currents of air reaching the lumber nor is there any possibility of 'any interference with the `continual lumber -drying process during the operation Iof the kiln. Since the outside air, during the lum-ber drying operation, enters only through the inlets in the ducts from which the air is being drawn into the end air chambers, the pressure of air in the kiln remains approximately the same as the atmospheric pressure outside. Asa result there is no possibility of too much outside air being drawn into the kiln at any time. Thu-s the amount of outside air drawn into the system during 'the operation of the kiln is automatically limited approximately to the amount of air which is lost or exhausted from the kiln, and the amount of air lost or exhausted from the kiln is controlled by the automatic operation of the ventilators 28 which in turn are operated by a well known temperature 'and humidity regulating control device.

The arrangement of Vthe ducts I6, Il, I3 and I9 reduces the number of fans required for circulating the air through the kiln and insures that all the air circulating through the syst-em will Apass .through the lumber. As a result the vol-unie of circulating air is elciently utilized and a corresponding amount of lumber drying can be performed in my improved kiln with a smaller supply of air than i-s the case with some of the other lumber ldrying kilns now in use.

A simple -set of switches enables the entire lumber drying operation of the kiln to be controlled very easily and simply by a single operator from a control room 25 .at one end of the kiln only, and finally adjustments to suit various conditions for `diierent types of lumber or for lumber in various stages of drying, can very easily be made merely by adiu'sting the temperature and humidity yaccordingly as desired. Conditions within the kiln for Iany one time during the continuous operation are always uniform.

I claim:

1. In a dry kiln of the character described, a celing wall, a row of transversely extending slot openings in said ceiling wall along each lside thereof, pairs of ducts located above and on opposite sides of `said ceiling and extending over said slot openings, each duct extending along the kiln from one end of the kiln, each duct having a roof sloping `downwardly from the end of the duct adjacent an end of the kiln to the opposite end of the duct, an yair chamber located above each end of said kiln and having a pair of ports connecting respectively with the pair of duct-s at that end of the kiln, a fan in each port. means for rotating said fans, means for controlling and reversing the rotation of said fans, the fan-s in the ports of each of said chambers so arranged and rotated that air will be drawn from one duct into the chamber and driven from the chamber into the other opposite duct, outside air inlets in the roofs of said ducts, means for opening and closing said inlets, a plurality of ventilators located along the center line V0f the kiln ceiling between opposite ducts, and means for opening and closing said ventilators.

2. In a dry kiln having a ceiling wal-l, a row of equally spaced, transversely-extending slot openings o-f identical size in said ceiling wall along each side thereof, pairs of ducts of similar size and shape loc-ated above and on opposite sides of said ceiling and extending over said slot openings, e-ach duct extending along the kiln from one end of the kiln, each duct having a roof -sloping downwardly from the end of the duct adjacent an end of the kiln t-o the opposite er1-dof the duct, an air chamber located above each end of said kiln and having a pair of ports connecting respectively `with the pair of ducts Iat that end of the kiln, the cross secti-onal area of each port being approximately equal to the tot-al area of the slot openings covered by the respective duct, a fan in each port, means for rotating said fans, means for controlling and reversing the rotation of said fans, the fans in the ports of each of said chambers so arranged and rotated that air will be drawn from one duct into the chamber and driven from the chamber into the other opposite duct, outside air inlets in the roofs of said ducts, means for -opening and closing said inlets, a plurality of ventilators loc-ated along the center line of the kiln ceiling between opposite ducts, and means for opening and closing said ventilators.

3. In a dry kiln having a ceiling wall, a row of slot openings of identical size in said ceiling wall along each side thereof, pairs of ducts of identical size and shape located above and on opposite sides of said ceiling and extending over said slot openings, each duct extending along the kiln from one end of the kiln to approximately the longitudinal middle of the kiln, each duct having a roof sloping downwardly from one end of the duct to the other, an air chamber located above each end of said kiln and having a pair of ports connecting respectively with the pair of ducts at that end of the kiln, a fan in each port, means for rotating said fans, means for controlling and reversing the rotation of said fans, the fans in the ports of each of said chambers so arranged and rotated that air will be drawn from one duct into the chamber and driven from the chamber into the other opposite duct, outside air inlets in the roofs of said ducts, means for opening and closing said inlets, said latter mentioned means operating to open the inlets of the ducts from which air is drawn into said chambers while closing the inletspf the opposite ducts, a plurality of equally-spaced ventilators located along the center line of the kiln ceiling between opposite ducts, and means for opening and closing said ventilators in unison.

4. A dry kiln of the character described including a ceiling wall, a row of transverselyextending slot openings in said ceiling wall along each side thereof, pairs of ducts of similar size and shape located above and on opposite sides of said ceiling and extending over said slot openings, each duct extending along the kiln from one end of the kiln, each duct having a roof sloping downwardly from the end of the duct adjacent an end of the kiln to the opposite end of the duct, an air chamber located above each end of said kiln and having a pair of ports connecting respectively with the pair of ducts at that end of the kiln, a fan in each port means for rotating said fans, means for controlling and reversing the rotation of said fans, the fans in the ports of each of said chambers so arranged and rotated that air will be drawn from one duct into the chamber and driven from the chamber into the other opposite duct, outside air inlets in the roofs of said ducts, means for opening and closing said inlets, a plurality of ventilators located along the center line of the kiln ceiling between opposite ducts, means for opening and closing said ventilators, baiiies extending a short distance downward in the kiln from the ceiling, parallel to the sides of the kiln and positioned beyond the inner ends of said slot openings, whereby to prevent the short-circuiting of air current in the top of the kiln, and means for heating the air currents.

R. A. SIMMONS.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 1,534,499 Braemer Apr. 21, 1925 1,745,375 Mueller Feb. 4, 1930 2,202,143 Cobb May 28, 1940 

